Various methods for delivering therapeutic agents are known. For example, therapeutic agents can be delivered orally, transdermally, by inhalation, by injection and by depot with slow release. In each of these cases the method of delivery is limited by the body processes that the agent is subjected to, by the requirement for frequent administration, and limitations on the size of molecules that can be utilized. For some of the methods, the amount of therapeutic agent varies between administrations.
A dermal micro-organ (DMO), which can be sustained outside the body (“ex vivo” or “in vitro”) in an autonomously functional state for an extended period of time, and to which various manipulations can be applied, may then be implanted subcutaneously or within the body for the purpose of treating diseases, or disorders, or for plastic surgical purposes. The DMO can be modified to express a gene product of interest. These modified dermal micro-organs are generally referred to as Dermal Therapeutic Micro-Organs (DTMOs).
Skin micro-organs (MO), including layers of epidermal and dermal tissues, for example; as outlined in PCT/IL02/0880, have been observed to be associated with a number of clinical challenges. Harvesting of a skin sample leaves a superficial wound on the patient that may last several weeks and may leave scars. The harvested skin sample requires significant processing to generate micro-organs from this sample. Also, implantation of skin micro-organs subcutaneously or deeper in the body have been found to result in the development of keratin cysts or keratin micro-cysts. Additionally, implantation of skin micro-organs as a graft onto the skin surface in “slits” requires significant technical expertise in order to handle the MO while maintaining its proper orientation.
Harvesting of dermis, e.g., to be used as a “filler material” in a plastic surgical or cosmetic procedure, is known in the art. Conventional harvesting techniques include using a dermatome or scalpel to peel away a layer of epidermis in order to expose a section of dermis. The dermatome or scalpel may then be used again to manually harvest the exposed section of dermis.
Another conventional apparatus for harvesting dermis, albeit not commonly used, is the Martin Dermal Harvester marketed by Padgett (Part No. P-225) for the indication of harvesting dermal cores from the back for subsequent implantation into the lips during cosmetic lip augmentation procedures. To operate this device, which is not commonly used, a sharpened cutting tube, which includes a reusable thick walled tube with an inner diameter of approximately 4.5 mm, is manually rotated at a very slow speed. Using this type of device generally requires applying pressure to the skin surface directly above the harvest site and installing sutures with active tugging as the cutting tube is pushed forward. Furthermore, the resulting harvested dermis is generally not uniform in dimensions and includes “plugs” of epidermis at either end of the dermal core.